1. Field of the Invention
The invention relates to a process for the internal coating of a hollow body.
2. Description of the Background Art
The coating of surfaces with thin functional layers, particularly within the nanometer range, with use of a plasma has been known for a long time. Different gas discharges under vacuum conditions are used in this regard. A distinction is made between physical and chemical vapor deposition.
The internal coating of tube material by plasma-assisted chemical vapor deposition represents a special challenge.
DE 10 2005 040 266 A1, which corresponds to U.S. Publication No. 20090155490, and which discloses a method for the internal coating of hollow bodies, in which a treatment area in a reactor chamber is evacuated at least partially, a process gas is introduced into the treatment area, particularly into the hollow body, and by means of radiated electromagnetic energy a plasma is ignited in the process gas introduced into the treatment area. In so doing, during the plasma treatment the process gas flows through the treatment area between opposite ends.
U.S. Pat. App. No. 2002/0058143 A1 discloses a combustion-based method for chemical vapor deposition (CCVD), in which the interior of a hollow body is coated by insertion of a flame burner.
A method for the internal coating of a hollow endless geometry is known from DE 10 2006 012 021 A1, which corresponds to U.S. Publication No. 2009092763, whereby a gas mixture containing at least one precursor is introduced into the endless geometry, whereby the endless geometry is passed through at least one electrode unit, whereby an alternating electric voltage is applied to the electrode unit, whereby the gas mixture is transformed at least partially to the plasma state in the area of the electrode unit, and whereby a reaction product is produced from the precursor by the plasma and deposited on the inner surface.
U.S. Pat. App. No. 2003/0215644 A1 discloses a method in which finely divided aerosols of polymer solutions are applied to a substrate, an energy source being applied simultaneously to the solution.
A CVD method is known from Japanese Pat. App. No. JP 04124273 A, in which the interior of a tube is evacuated and a carrier gas with gaseous raw materials is introduced. A plasma is generated by arc discharge and passed through the interior of the tube by central/axial guidance by means of magnetic field arrangements for the purpose of CVD deposition.
DE 197 26 443 A1, which corresponds to U.S. Pat. No. 6,129,856, and which discloses a method for surface-finishing inner surfaces of hollow bodies with at least one opening, said method in which the hollow body is finished from inside by a hollow-cathode glow discharge as the excitation source, and a gas stream flowing through the hollow body extracts particles from a plasma forming during the hollow-cathode glow discharge, excites them, and transports them to the inner surface of the hollow body where they initiate the finishing process, whereby the hollow body is disposed in a vacuum vessel, and the hollow body and the hollow cathode form elements separate from one another.